ConstructHTDPTranformation – Global Mapper

WRAPPER_API DatumTransform* ConstructHTDPTranformation(const 
 HorizontalCoordSys& inputCS, const HorizontalCoordSys& outputCS, 
 double inputEpoch, double outputEpoch) const;

Description

This method is used to construct an HTDP transformation between two input coordinate reference systems. In order for the transformation to be properly constructed, both coordinate systems must be using an HTDP compatible base geodetic model. This is determined by the identification string on the Horizontal Datum used by the coordinate system In order to use the HTDP transformation methodology, the coordinate system must be built on one of the following base geodetic coordinate systems:

IGb00 Coordinate System
IGS00 Coordinate System
IGS05 Coordinate System
IGS97 Coordinate System
ITRF 00 Coordinate System
ITRF 05 Coordinate System
ITRF 88 Coordinate System
ITRF 89 Coordinate System
ITRF 90 Coordinate System
ITRF 91 Coordinate System
ITRF 92 Coordinate System
ITRF 93 Coordinate System
ITRF 94 Coordinate System
ITRF 96 Coordinate System
ITRF 97 Coordinate System
MARP00 Coordinate System
NAD83(1986)
NAD83(NSRS2007)
NEOS90 Coordinate System
PACP00 Coordinate System
PNEOS90 Coordinate System
SIO_MIT92 Coordinate System
WGS 72
WGS 84
WGS84_G1150 Coordinate System
WGS84_G730 Coordinate System
WGS84_G873 Coordinate System

The Epoch date used in the construction of this transformation is a decimal year format. For example, 1999.12345 represents the year 1999 with an additional 12.345% of the year. Since there are 365 days in 1999 (it's not a leap year), that would be 45 days, 1 hour, 25.32 minutes into the year, or Feburary 14th 1999, at 0125 in the morning. The TimeUtil class provides simple methods for converting the epoch time values from standard date, month, year, and time.